Hydraulic system for controlling the operation of rotary hydraulic motors



Feb. 8, 1949. R. K. JEFFREY HYDRAULIC SYSTEM FOR CONTROLLING THE OPERATION OF ROTARY HYDRAULIC MOTORS 2 Sheets-Sheet 1 Filed July '7, 1944 {NVE/V702 RQBERT K. JEFFR Y FLnRr- NCE HL. JEFFRLY. Exacumx.

Dfcuscn.

R.' K. JEFFREY 2,461,116 HYDRAULIC SYSTEM FOR CONTROLLING THE OPERATION OF ROTARY HYDRAULIC MOTORS Filed .my fr, 1944 z sheets-sheet 2 Feb. s, 1949.

l INVENTOA RQBERTKJEFFRLY. Dfcwm. BY FLORENCE H.C.JEFFR&Y, fxecum/x,

' UNITED Patented Feb. 8, 1949 STATES PATENT OFFICE HYDRAULIC SYSTEM FOR CONTROLLING THE OPERATION F ROTARY HYDRAULI MOTORS Robert K. Jeffrey, deceased, late of Bexley, Ohio, by Florence H. C. Jeffrey, executrix, Bexley, Ohio, assignor, by mesne assignments, to The Jeirey Manufacturing Company, a corporation of Ohio Application July 7, 1944, Serial No. 543,788

Claims.

tors of a lvehicle either in series or in parallel vor in series parallel.

Another object of the invention is an improved and efficient system of control -of a fluid pressure motor connected to a traction wheel of a vehicle to drive the same or to act as a brake when thetraction wheel drives the motor as a f pump.

. vehicle, including a reversing switch for the motor to effect braking of the vehicle either by neutral setting of the reversing switch or by moving the latter to reversing position while the vehicle is in motion.

A further object of the invention is the prol,vision of a reversing switch for the rotary hydraulic motor connected to a traction wheel of a vehicle to drive the latter forwardly or rearwardly.

Another object of the invention is the provision of a supercharging pump in a fluid pressure Avehicle controlling system for replenishing fluid pressure medium, such as oil, lost therefrom through leakage, and to replace heated fluid pressure medium in the system.

y A further object of the invention is the pro-y vision of an improved and elllcient system of control for rotary motors connected to a vehicle to drive the same, so that the pump supplying .oil to the motorsV may be operated continuously or without interruption during starting, slowing down, stoppingand reversing the travel of the vehicle.

vAnother object of the invention is the provision fina system of control of rotary motors connected rto a vehiclejto drive', the same, of means for effecting brakingof the vehicle by the motors actling as pumps evenwthough the supply pump is no (ci. fio- 53) longer operating due to the discontinuance of operation of the engine driving said supply pump. Other objects of the invention will appear hereinafter, the novel features and combinations being set forth in the appended claims.

In the accompanying drawings,

Fig. 1 is a plan view of a vehicle including the invention; Y 1

Fig. 2 is a side elevational view of the vehicle ofEig. 1; and y Fig. 3 is a piping diagram of the hydraulic system for controlling traction motors mounted on the vehicle wheels.

This application is a continuation in part of co-pending application, Serial No. 407,166, filed August 16, 1941, now Patent 2,357,742, dated September 5, 1944, for an improvement in a vehicle.

Referring particularly to Figs. 1 and 2 of the drawings, there is illustrated a vehiclev in the lform of a coal carrying shuttle car which includes the preferred embodiment of the invention. 'I'his vehicle or shuttle car comprises a body I0 which is formed by opposite sloping side walls II, II forming a receptacle for the ma.- terial to be carried, such as coal, which sloping side walls lead to spaced vertical walls I2, I2 between which there extends a bottom plate I3. The bottom plate I3 formsthe bottom of the material receiving receptacle and of a conveyor which includes endless chains I1, Il which extend between rear end drive sprockets carried by drive shafts I8 and idler head sprockets at the front of the vehicle. Transverse flights I9 are interconnected between the endless chains I 1 to form the complete conveyor generally designated by the reference character 20. It is evident that v material may be discharged from the car by driving the upper run of the conveyor 20 forwardly,

is ultimately power operated from said motor 2I.

One end of the armature shaft of the motor 2| is connected through a clutch 22 which is operable from an operators station 23 by an appropriate pair of foot levers 22', 22" preferably interconnected so that the operator may face Aeither forwardly or rearwardly while riding on the seat 24. From the clutch 22 a gear train 25 extends through reduction mechanism 25" to the drive shaft I8`of the conveyor 20.

The motor 2I also drives hydraulic pumps 26, y

28', for supplying hydraulic iiuid under pressure which is employed to drive the traction wheels of the vehicle. to steer the vehicle and also to contgl the hyduraulic motor 28 of electric cable reel The shuttle car or vehicle l is also provided with four wheels 29, 30, 3| and 32 which are preferably all traction wheels and preferably all steering wheels. Each of these wheels isof similar construction except for certain reversal of parts which is obvious from Fig. 1 of the drawings.

Referring particularly to Figs. 1 and 2 of the drawings, it will be seen that steering of all of the four wheels 29, 30, 3i and 32 is eil'ected by a single hydraulic piston motor 33 which is connected by a longitudinally and forwardly extending rod 34 and by a longitudinally and rearwardly extending rod |34 interconnected by a pivot arm 35 to the forward and rearward pair of wheels which are pivoted about upwardly extending axes, the forward wheels and rearward wheels each being interconnected by steering mechanism including transverse tie rods 38 and 31, respectively, the opposite ends of each of which are connected to arms rigidly attached to the stub axle of the associated wheel; the arms associated with the tie rod 35 being seen at 33 and 39, respectively, and being associated. with wheels and 29, respectively.

The arms rigidly attached to the stub axles of the wheels 29 and 32 are designated 39 and 39' as shown in Fig. 1. The arms rigidly attached to the stub axles of the wheels 30 and 3i are designated 38 and 38'. Connected rigidly to the stub axle of the wheel 30 is the additional arm 34' which is pivotally connected to the front end of the rod 34. Connected rigidly to the stub axle of the wheel 3|` is the additional arm |34' which is pivotally connected to the rear end of the rod i34. Since the two armed lever is pivoted midway between its ends to the pin 35' which is xed to the vertical plate l2, any longitudinal movement of the piston rod of the hydraulic piston motor 33 will tilt the lever 35 on its iixed pivot 35' and move the rods 34 and |34 in opposite directions to eiect swinging of the front pair of wheels and the rear pair of wheels in opposite directions, as illustrated in Fig. 1 of the drawings.

The wheels 29, 30, 3| and 32 may be of any conventional construction and may even embrace a type of wheel adapted to run on a track or a wheel adapted to drive an endless crawler such as of the Caterpillar type. As previously indicated, each wheel 29, 30, 3i and 32 is mounted upon a stub axle which includes within its construction a hydraulic engine 45 which is preferably operable either as a motor to drive the wheel or as a pump to be driven by the wheel. Each stub axle also includes within its construction at least part of a speed changing mechanism interposed -between the engine 45 and the wheel. The entire -mechanism comprising the wheel, hydraulic engine 45, and speed changing mechanism is mounted as a unit for swinging movement about an inclined upwardly extending axis to provide for steering o! the vehicle as previously mentioned, and the entire mechanism is shown, described and claimed in the parent application, now Patent 2,357,742, above identied.

Four brackets -48 are each rigidly attached to the frame of the vehicle and specifically to spacers 41 which in turn are each rigidly attached to 'aA wall i2. Brackets 49 each carry a pivot pin,

' of wheels and steering to the other pair.

4 f not here shown, which extends upwardly and is preferably slightly inclined inwardly to the vertical. These pins each pivotaily carry one of the stub axles of a wheel 29, 30,' 3| or 32 for steering movement.

Each hydraulic engine 4.5 includes a rotor, swash plate, pistons and associated mechanism, and for the precise structure of these elements reference is made to the patent to Robert K. Jeffrey, 2,331,694, granted Oct. 12, 1943, for an improvement in a Hydraulic pump or motor.

It is here pointed out that each engine 45 is reversible and each engine 45 includes two ports for hydraulic fluid either of which may be the supply port and the other the exhaust port, depending upon the direction in which the rotor of the engine 45 is to be driven to drive the wheel. When the rotor of engine 45 is being driven to drive the wheel the engine is, obviously, acting as a motor and when the wheely is driving the rotor, such for example as when the vehicle is coasting, the engine 45 is acting as a pump and by throttling the output thereof the engine or pump may be employed as a brake for the wheel.

In the operation of the vehicle it is evident that in the preferred embodiment of the invention all four wheels are traction wheels as well as steering wheels, though it is, of course, evident that as to certain aspects of the invention traction may be-limited to either the front wheels or the rear wheels, and steering may likewise be limited to either the front wheels or the rear wheels, and the traction may be on the same pair of wheels or traction may be applied to one pair It isl preferred, however, to have all wheels both trac'- tion and steering wheelsas this reduces the necessary size of any hydraulic engine associated with a traction wheel and also makes possi-ble the turning of the machine in a minimum of space.

Referring now to Fig. 3 showing the hydraulic system for controlling the traction motors 45, the various operations will be described. A variable volume pump 26 is employed in the system and may be connected to be driven from the armature shaft of the electric motor 2l either through the constant volume gear pump 26 or by means of gearing extending laterally from the armature shaft independently of the pump 26. For convenience in illustrating, the pump 26 is shown in Figs. 1 and 2 as coupled directly to the arma'- ture shaft by means of a shaft protruding from the gear pump 26.

While the variable volume pump 26' may be of the adjustable swash plate type arranged as shown in the co-pending application of Robert K. Jeirey, deceased, S, N. 498,087, led Aug. 10, 1943, now Patent No. 2,452,760', for an improvement in Mining machines, the self-centering pump disclosed in the De Millar Patent No. 2,057,089, granted Oct. 13, 1936, for an improvemerit in Hydraulic road grader, is shown in Fig. 3 of4 the accompanying drawings to simplify the disclosure herein.

This self-centering variable volume pump 26' comprises a casing 3I0 having at diametrically opposite sides thereoi.' a plunger 3H adapted to be acted on by hydraulic pressure, and a plunger 3i2 acted on by the spring 3i'3 in the cup 3l4.

Between the plungers is the ring 3I5 which when in its position of greatest eccentricity effects maximumpumping. When the pressure in the supply pipe 316 becomes excessive the hydraulic pressure through the branch pipe 3I'I on the plunger 31| edects centering o! the ring 3|5 against the action of the spring 3|3.

A supercharging pump 315 ofrelatively low capacity and low pressure is arranged as shown in Fig. 3 to draw oil from the supply tank 231 through' the illter 3|3 in suction pipe 3| 3 and deliver such oil through the check valve 323'intc the suction pipe 32| which is connectedl to the bottom of the pump 23'. The variation inthe volume of delivery from the pump 23' is'entirely automatic and is dependent upon variations in hydraulic pressures in the supply pipe 3|3 due to various conditions surrounding the operation of the vehicle by means ci' the traction motors 45 connected to the vehicle wheels.

The motors 45, one mounted on each of the four wheels, may all be connected in parallel for low speed of travel of the vehicle and in series parallel for high speed of travel. In Fig. 3 the motors 45 on each side are arranged in series parallel.

6 When the slide valve 321' is in central position. -iree wheeling of the vehicleA may be had. This is a desirable feature to facilitate towing oi the The series parallel valve mechanism 322 comprises a slide valve 322' which has two positions, one at the right for parallel connection oi the motors 45 and the other at the left, as shown for series parallel connection of all of the motors 45.

The ends of the valve chests 324 may be pro-` vided with hydraulic cylinders, and the ends of the slide valve 322I may constitute pistons 325 and 325 adapted to reciprocate in such cylinders. It will thus be seen that the slide valve 322' may be shifted' to series parallel position when the piston 325 is moved to the left to series parallel setting and by acting on the piston 323 the valve 322' may be shifted to the right to parallel setting.

A three position pilot valve mechanism 321 is arranged to control the operation of the series parallel valve mechanism 322. When the slide valve 321 is in its right-hand position the supply port 323 is connected through the annular channels 340, 329' and 333 to the port 33| and the pipe 332 which is connected to the hydraulic cylinder at the left-hand end of the chest 324 of the series parallel valve mechanism 322. Therefore, when the slide valve 321' of the pilot valve mechanism 321 is moved to the right, the seri/es parallel slide valve 322' will be moved to the right to parallel position.

When thus moved to the parallel position the piston 325 will be moved to the right to force the oil out of the cylinder in which the piston 325 moves. The oil which the piston 325 thus forces out passes into the pipe 333 and thence into port 334 through annular ports 335, 335', 331 into port 333 and exhaust pipe 333to the supply tank 231.

When the slide valve 321 is moved to its lefthand position the -supply port 323 will be connected through the annular channels 345, 333-and 335 to the port 333 and thence through the pipe 333 to the cylinder to the right of the piston 325. Therefore, when hydraulic pressure is exerted on the piston 325 at the right-hand o f the slide valve 322 the-latter will be tmoved to the left t its series parallel position.

The slide valve 321' when moved from either the right or left-hand position to the central or free-wheeling position does not cause the series parallel slide valve to shift its position, but it blocks the ports 333 and 335 to lock oil in the hydraulic cylinders of the series parallel valve chest 324, thereby locking the slide valve 322' in that position in which it was last set.

vehicle. In that event the motors 45 on the vehicle wheels will be driven as pumps and a circuit established by the central position o! the valve 321 tor free ilow oi the oil.

Assuming that the vehicle is being towed and that the pipe 353 is the pressure or exhaust side oi.' the wheel motors, the pipe 355 will be the suction side. The circuit for the motors 45 under these conditions will be from pipe 353 to pipe 335 and thence'through check valve 313 t0 pipe 33|, and the core 321' being in the central or free-wheeling position, the oil ilows throughv tank 231 by way of pipe 3|3 including lter 3|3 md pipes 343, 314, 333, 333, check valve 315 and' pipe 334 to pipe 355. Pipe 333 may also receive oil from pipe 333 through pipe 314.

If the pipe 335 is the exhaust or pressure side of the motors and the pipe 353 the suction side while the vehicle is being towed and the motors nected in series parallel.

are connected in parallel the tractive capacity will be greater, but the speed will be one half of that obtained when all the motors 45 are connected in series parallel. This can readily be understood 4by assuming any given volume of .delivery o! the main pump 26' and taking into consideration the volume oi flow through the motors 45. The speed of the motors is dependentv upon volume of ilow therethrough and consequently when the motors are in parallel, one quan 'ter of the pump delivery will ilow through. each motor, resulting in less speed than when only.

half the volume oi pump delivery ows through each motor when connected in series parallel.;I ,The connections for the motors 45, as shownih Fig. 3, vprovide differential action between the driving wheels and give a positive four whel drive when all the motors` are in parallel.

Before the vehicle is stopped the connection of motors is brought back to parallel, from being in series parallel. Consequently, when the vehicle .is at rest under'these circumstances, the slide valves 322' and 321' will be in their right-hand positions with slide valve 322 held there by -a holding circuit including the pipe 332. Even when the motors 45 are driven as pumps to secure bralt-- lingV of the vehicle, the pumping action will pro5 duce a pressure on the piston 325 when the slide 321' is in the leit hand position as shown, or upon the piston 325 when the slide 321' is in the right hand position to hold the slide valve 322' in its proper position.

The throttle and reversing valve mechanism 34| has three positions, including the neutraler central position shown in Fig. 3. In this central or neutral position a no-load by-pass circuit is established for the main pump 26'. The supply pipe 3|5' receives oil under pressure from the 'pump n' through pipe als and extends to the 7 pcrtlllwhichisconnectedtotheannuiarehannel3l3andthelatteriscmneetedbytheradial pamgesllltotheinnercylindriealreceul. Prom the recess 333 the liquid is free to pas throughtheradialpassagewaysillintothepassagewayluandthencethroughtheportulinto theretmnlineultothesuetionpipelll. The pump It'maythereforebeoperated continuomy' evenwhenthevehicleisatrestandthismay bedonewiththe consumptiouofverylittlepower astheeiectricmotorli eonnectedtothepump 'todrivethesamemaysimplyidlewhenthe vehicleisatrestwiththereversingvalvemecha- 'nism 33| in neutral position.

When the throttle and reversing slide valve 33|' Lsmovedtotherightthesupplyprtuwill beconnectedthrwghtheannuiarchannelsm. 33| and 33| to the port 332. Then the oil iiows through the pipe 333 into the annular port 334. Iithe series parallel slide valve 322' at this time. lain its left-hand or series parallel position, the oil will continue to iiow through the pipe lil inse the motors on the wheels 2l and 32 and thence through the pipe 333 into the annular porc 351. Since the slide valve 322' is in series parallelposition the oil will continue through the hole 333, the cylindrical recess 333 and hole 333 into the annular port 33| and thence through the pipe 333 and the motors l! on the wheels 33 and 3| into the pipe 333 which is connected to the an 30 nular port 334. A pipe 333 connects the port 3 to the port 333 which leads to the annular port 331. Since the reversing slide valve 33|' is now in its right-hand position, the oil continues through the annular channels 333 and 3i! inter-35 the passageway 331 which is connected by means of the port 333 to the return pipe 33S and the suction pipe 32| of the main pump 2i'.

Itwillthusbeseenthatwhentheslidevalve VIl will receive ono-fourth of the total volumeoioiiilowinginpipet Theslidevalve 322' wheninits righthand positionaiso connects portsiandlwherebyoiliiowingthercln irnthewheel motors llisadmittedtopipe'lil and'isnormaily returned tothe main pump 23'.

Itwiiiheseenthatupcnareversaloitheposi-l tion or slide 33|' oi' reversing and throttle valve 33| the ilow of oil to and through the wheel motorswillbereversed.

Whenitisdesiredtostopthevehicleitmay motors 45 will be relieved through valve 313. The Iehicle will then be decelerated at a constant rate until it comes to rest.

As illustrated in Fig. 3, the motors are in series may be eiiected whether the vehicle is traveling forwardly or rearwardly. During such braking operations by reversal, the pump 26 is endeavoring to drive the motors 4I as such in a direction opposite to the direction in which the vehicle is traveling while at the same time the momentum of the vehicle is attempting to drive the motors 4i as pumps. The motors I5 thus eiiect 'a throttling action to the iiow from the pump II' and the increase in hydraulic pressure in the supply line 3| i' will automatically eii'ect center- 323' of the series parallel valve mechanism 322 ing oi' the Dump 25' t0 decrease the ilow. This is in its left-hand or series parallel position and the reversing slide valve 33| is in its right-hand position, the main pump 23' will be connected up to the rotary hydraulic motors 0n the vehicle wheels with all of these motors inseries parallel,-45

the circuit being such that the total volume of oil iiowing to the wheel motors l5 is iirst divided betweenthemotors ofwheels!! and 32 andupon passing therethroughismergedintheserics par- ,so allel valve and then redivided between the motors of wheels 3l and 3|.

Now by moving the slide valve 33|' to its leithand position. the iiow from the pump Il' throughthemotorsllwillbereversed. Thiscan muy be Seen bv leaving the suse valve m' x11-:55

Vconnect the annular ports 33| and 31|. Then Y andinthateventtheiiowoioilwillheiirst throughthemotors oithewheels 3land3i. agd then through the motors ot wheels 23 and 3.

When the wheel motors are to be operatedor` connected in parallel the slide valve 322' is shifted to the right by moving the slide valve 321' oi pivot valve 321 to the right and assuming that the slide 33|' of the throttle and reversing valve 33| is positionedso that pipe lll is under pressure from main pump 23 a circuit for the motors is established from pipe 353 .through port V333 to port 35| whereby the total volume of oil iiowing from pipe 333 is divided between pipe 333 leading h the action either with the type of self-centering pinnp 2i' as shown 'in Fig. 3 or with the tilting swash plate type of variable volume pump.

0n the level or up grade the operator of the vehicle can readily stop the vehicle by reversal o! the slide valve 3M' and then move the latter to neutral position for park braking; then the motors 43 will he locked since the oil therein will be blocked of and circulation can take place only by overcoming valve 315.

If the reversal braking operation takes place onfa down grade and the motors are actually driven u pumps in opposition to the main pump 23', the return line 333 may receive more oil ilow than the suction pipe 32| can accommodate. in which event the iiow will betaken care of by the check valve 312 which is adapted to open from the return pipe 348 into the supply pipe 3|3'.

It; due toa down grade travel of the vehicle. the motors Il over-run the pump 26', the excess volume will pass through the check valve 312. Make up oil from supercnarging pump 3|3 iiows into pipe 343 to replenish the oil lost from the circuit by leakage.

The relief valve 313 is provided as a safety to the auxiliary pump 3I3. This relief valve also provides means for taking a small quantity of hot oil from the semi-closed hydraulic system so that pump 3|3 can replenish the system with 7 fresh cool oil.

Actual stopping ot the vehicle may be eiiected either by using reverse directional positioning of thevalvel' orbythe centeringthereoias above Y explained. When centering the valve mechanism tumours anneau amzanaplpem mm "5 au. man; may be erected by movement of When the reversing valve 34|' is in neutralv position and the vehicle by its momentum is driving the motors 45 as pumps, passage for the oil through the high pressure relief valve 315 is afforded by either of the two pairs of check valves 313, 313 or 313, 311 and thel pipe 33|, relief valve 315, pipes 382, 383 and 330. The pipe 385 is connected 'to the check valves 313, 311 between the same by being connected to the pipe 384. The pipe 353 is connected to the check valves 318, 319 between the same by being connected to the pipe 335.

v.All of the check valves 313, 311, 313 and 313 open toward the right as viewed in Fig. 3. If the reversing valve mechanism 34|' is closed too suddenly while the vehicle is traveling and the motors 35 are driven as pumps by momentum of the vehicle, the flow of oil may be either from the pipe 353 intothe pipe 335 or from the pipe 335 into the pipe 334. If pipe 353 is the supply pipe, the check valve 319 will open and permit flow into pipe 33| and thence through the high pressure relief valve 315 into the pipe 332 which is connected to pipe 333 and the pipe 333 which is connected to the supply tank 281. The suction line for the motors 45 acting as pumps will then be pipe 380 which is connected to receive oil from pipe 332 and supply tank 281 through pipe 383, checkvalve 313, -pipes 334, 335, annular port 363 to pipe 333. Y

If pipe 355 is the supply pipe from the motors 35 acting as pumps, 'the passage through the relief valve 315 will be by way of check valve 311 and pipe 38|. The suction line will be established by pipe 380, check valve 313 and pipes 335, 353 through annular Iport 354 to pipe 355.

In order to avoid sudden reversals of the slide valve 34H a lever 383 of vextra, length may be pivotally mounted and connected thereto as shown in Fig. 3. Two such levers may be interconnected so that thedriver on the seat 24 may 'face either forwardly or rearwardly in position to easily actuate either lever 335, as shown in Figs, 1 and 2. In a similar manner, the levers 381 are interconnected and ilexibly attached to the slide valve 321' for operation thereof.

The hand rail 338 is for the convenience of the operator. By grasping the hand rail 338-with one hand the operator may more readily retain his seat 24 while operating the levers shown in Figs. 1 and 2; either lever 22', 22" being for operation of the steering mechanism, either lever 381 being for operation of the pilot valve 321 to control the series parallel valve mechanism 322, and either lever 386 being for operation of Vthe reversing valve mechanism 34|.

In order that the oil in the reservoir 231 may be cleaned continuously so long as the motor 2l is running. an additional'iilter 383 is provided in the by-pass pipe 330 as shown in Fig. 3; It will thus be seen that the supercharging pump 3|8 may draw oil through the supply tank- 231 through the filter 3|'9 and by-pass some 4of it through the ilter 383 in the pipe 390 at alltimes,

. secure breaking action, the sunerelierging-p'umpfy *i is embodied in they system.4

are included in the present applicatien'utpillus-fY particularly when the vehicleis the motor 2| is kept While the supercharging'p' secure illtering oi' the oil returned tank 231 and to replenish-'jo tors45areofthetypeshovi'rnv ,l A 4 ent No. 2,331,694 above referred Vt f,vi'rherein ther are springs within the pistons oiugtli :notruf`` provide 'for the positive suctionjlorrintakejo 1 through the intake or suction portf ofnthei l I f Such springs or their equivalen are nec ry if the supercharging pump 3|8" niitte'd'b anse when the motors 45 are 'driven as d H mentum of the vehicle, nohy aulicp'ressuref" would be available to keep thepistos off" the mo tor in contact with the swash'plate.` llifhen'thel motors 45 do not include any mechanismffr lri'old'-I f ing the plstons' in contact"'"'vv'ithjtlefswashv plate while the motors are serving as'gpumpsftof 3 3 should be included in the system Buchsup'e'r charging pump 3|8 may be conn" ted'bygearing tothe shaft of the motor 2|. n It is therefore preferred to inclu 4the super charging pump 3|8 in the system hat any type ofrotary hydraulic motor maybe used; thatfisf to say, the system illustratedV in 3,"including the supercharging pump 3|8, is preferredbefr` ff cause of its almost universal adaptatio'nto avehiv cle having rotary hydraulic motors" connected 'f' its wheels, so that the motors mafybe'gin'anyf'jf event, driven as pumps to permit the' elimination of mechanical brakes of the brakeafbandtype.V ,n While the apparatus shown'inlFi W i inclusive, is described and claimedin the par application, Serial No. 407,166j.ffiled Air'gustfIB A 1941, now Patent 2,357,742, datedsptembrfgff 1944 for an improvement in Vehiclestiieseiviews f trate more clearly one use of t draulic system. I' A' It should also `be noted that" t gear reduction between the rot f?. motor and the wheel, the morele eciii park braking action and the easierE vehicle to move away from its sta for instance, up grade. Inth1 greater the gear reduction the apparatus.

It is therefore preferable to gear reduction between the engin cause of -the kavailability of gr getting started up grade and place to place in the mine. n For the steepest down grade y,ther wheeling and more brakingactin undue speed when the greater grades are not so steep the'fr increased because less 'brakin ent.

The pipes 353 and 365 are t motors acting as pumps. If th 34| is in neutral position when h pumps, the local circuit for through the relief va1v'e 315.",1f ,he left in its running position wired-rt 11 begiwactaspummtneywmmmoppiuon tothemainpump'.withtheresultthattheoil will spill over into the pipe 333 and flow through pipe 339 into the supply tank 2.1. In this operation hot oil from the motors W is cooled in the tankandmayberesuppliedtothemainpump 2l' by the super-charging` pump 3i3.

Il the vehicle is slowed down by movement o! the slide valve 3ll' to reversal from its running position, the pumping of the motors will be added to that of the main pump 23', with the mult that the low pressure relief valve 313 will be opened in the direction of the arrow 3M because more `oil enters the return pipe 3&9 than can be taken care of by the suction pipe 32| and valve 312 is retained closed by pressure in pipe 3N.

In the event that the pumps 26' and 3|3 should become stalled by the stopping of the electric motor 2|, and the motors l5 should be driven as pumps by the momentum of the moving vehicle, the check valve 312 may come into play as follows. Assuming the valve 323' in series parallel position. as shown in Fig. 3. and the valve 3M' in its right-hand position. oil will ilow -from the pump 2B' into pipe 355 and through all the motors 65 in series parallel, the return iiow being to annular channel 333 and return pipe 34S. When pump 26' becomes stalled and the motors 45 act as pumps, the oil supply from pump 26 in pipe 3i6' is cut oil and relief is afforded by the oil flowing from pipe 343 into pipe 3N through check valve 312 and thus substantially a no-load circuit for the motors l that by-passes the pump 26' is established.

Now if the operator should attempt to slow down the vehicle gradually by movement of the valve 3H' toward the left to its central or neutral position the oil flowing in the by-pass circuit including check valve 312 will be restricted by the gradual closing oi the port 368 and a braking effect on the motors I5 acting as pumps will be had. Should the position of valve 34|' be changed too rapidly and the pressure in pipe 355 increase above the pressure required to operate valve 315, the circuit including check valves 31S,

311, pipes 38|, 332, check valve 315, pipe 380 and check valves 31S, 313 will become eifective with the valve 315 acting to limit the maximum braking effect that will be applied to the wheel motors 65. The throttling action oi the valve 31 will finally eilect park braking because then the motors are locked by the terminal pipes 353 and 355 at the ports 353, 363. It will be seen that regardless of whether pipe 353 or 365 is the pressure or exhaust pipe from the wheel motors l5 acting as pumps, the braking circuits will be established similar to that described with the valves 31|' and 315 in control.

Obviously those skilled in the art may make various changes in the details and arrangement of parts without departing from the spirit and scope of the invention as deilned by the claims hereto appended, and it is therefore wished not to be restricted to the precise construction herein disclosed.

Having thus described and shown an embodiment of the invention. what is desired to be secured by Letters Patent of the United States is:

1. Apparatus of the class described comprising in combination means including a rotary fluid pressure motor. a variable volume pump comprising means for automatically controlling the volume o! delivery therefrom in accordance with variation in the supply pressure, valve mechanmedium from said pump to said motor. means associated with said valve mechanism for estab lishingaclosedlocal circuitforsaidmotorto lock the latter in position for park braking of the motor. and a relatively high presure relief valve insuchlocalcircuittoeifectgradualstoppineof said motor .when said valve mechanism is moved to neutral position.

2. Apparatus of the class described comprising in combination means including a reversible rotary hydraulic motor, valve mechanism connected to said motor to control the direction of rotation thereoi'. means associated with said reversing valve mechanism for establishing a closed local circuit for said motor when said valve mechanism is moved to neutral position, a relatively high pressure relief valve in said local circuit, and two pairs of check valves in said local circuit, one pair in parallelism with the other pairandallcheck valves adaptedto openinthe same direction. the construction and arrangement being such that one terminal of said motor is connected to one pair of check valves between the same and the other terminal of said motor is zconnected to the other pair of checknvalves between the same so that irrespective of the direction of rotation of said motor when driven as a pump by momentum a circuit will be completed through one of each pair of check valves and said $0 relief valve when the hydraulic pressure of the motor acting as a pump exceeds a predetermin value.

3. Apparatus oi the class described comprising in combination means including a plurality of V rotary hydraulic motors, valve mechanism for connecting said motors in series or in parallel, hydraulic motor mechanism for operating said valve mechanism. pilot valve mechanism for controlling said hydraulic motor mechanism 40 to effect connection of said motors in series or in parallel, and reversing valve mechanism for controlling the direction of rotation of said rotary hydraulic motors.

4. Apparatus of the class described comprising in combination means including a plurality of rotary hydraulic motors, valve mechanism for connecting said motors in series or in parallel. motor mechanism for operating said series parallel valve mechanism in two positions one for series connection and the other for parallel connection of said motors, pilot valve mechanism for controlling said motor mechanism, said pilot valve mechanism having two positions one corresponding to the series connection of said motors and the other corresponding to the parallel connection thereof. a three position reversing valve mechanism connected to said motors to control the direction of rotation thereof whether connected in series or in parallel, and means associated with said reversing valve mechanism in neutral position for establishing a braking circuit for said motors when driven as pumps by momentmn while said series valve mechanism remains in one of its two positions and while Saidpilotvalveremainsinoneof its two positions.

5. Apparatus of the class described comprising in combination means including a plurality of rotary hydraulic motors, reversing valve mechanism for controlling the direction of rotation of said motors, valve mechanism for connecting said motors in series or in parallel, motor'mechanism for operating said series parallel valve mechanism. pilot valve mechanism for controlling said ism for controlling the supply of iiuid pressure 76 lastnamed motor mechanism, and means associated with said pilot valve mechanism for establishlng holding-circuits for' said motor mechanism to hold the series parallel valve mechanism in its adjusted position both when said rotary motors are operated as motors and when operated as pumps by momentum.

FLORENCE H. C. JEFFREY.

Ezecutrim of the Estate of Robert K. Jeffrey.'

Deceased.

REFERENCES CITED The following references are of record ln the flle of this patent:

UNITED STATES PATENTS Rayburn Apr. 18, 1933 Number Number Name Date Greist Mar. 13, 1934 Muller June 5, 1934 Adams Oct. 16, 1934 Montelius Jan. 15, 1935 Fjellstedt Apr. 30, 1935 Douglas .Oct. 6, 1936 Kennedy Nov. 10, 1936 Centervall July 13, 1937v Y Kempthorne July 20, 1,937 Flowers Mar. 8, 1938 Thoma June 6, 1939 Sheridan Jan. 14, 1941 Lee Sept. l2, 1944 Swanson f.- July l0, 1945 Baldwin Sept. 11, 1945 4 FQRIGN PATENTS 

